What if 80% of the album is a "solo"? These guys use sweep pick arpeggios just for riffs (not solos) on both bass and guitar. Dude does these monster sweeps and tap runs on an 8 string too.
If you play guitar they are worth checking out, even if you don't like the style, just for the technicality. Tons of live vids of them on YouTube and they pull this shit off clean as hell live.
Honorable mention to Viraemia. Some of the most brutally technical shit ever. I mean, the bass line is harder than 99% of bands guitar solos: